Many portable electronic devices, such as cell phones, tablet computers, or multimedia players, usually include circuit boards. Passive components of a circuit board, such as resistors or capacitors, are usually embedded in a substrate of the circuit board in order to decrease the thickness of the portable electronic device. During manufacturing, the passive components are disposed between two resin layers, and the two resin layers are pressed and connected to each other, thereby embedding the passive components in the two resin layers.